Actual message (from photo, not recorded in
dnf system-upgrade log -1):
Upgrading : glibc-2.23.1-18.fc24.x86_64 28/4874 warning: %trigger(cronie-1.4.12-1.fc21.x86_64) scriptlet failed, exit status 127 Non-fatal <unknown> scriptlet failure in rpm package glibc
It looks like the problem is some interaction between glibc for Fedora 24 and cronie for Fedora 21. Is this a problem?
sudo dnf reinstall glibc worked fine, by the way.